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by Zhang, Fen, Ph.D., STATE UNIVERSITY OF NEW YORK AT STONY BROOK, 2009, 307 pages; 3405931

Abstract:

Nanomaterials have attracted considerable attention due to their unique physical properties and potential applications as building blocks in nanoscale devices. In particular, the intrinsic anisotropy inherent in one-dimensional (1D) nanomaterials renders them the smallest dimension structures that can be utilized for the efficient transport of electron and optical excitation. The template-directed synthesis technique represents the most straightforward and versatile route for achieving 1D growth. However, there are still challenges including (1) the development of an environmentally-friendly synthetic method, (2) a deep understanding of the relationship between size, composition, and physical properties in 1D nanostructures, (3) the design of 1D nanomaterials with novel properties, and (4) the application of 1D nanostructures in various fields, such as energy, catalysis, and biotechnology. Hence, the synthesis and characterization of 1D nanostructures, as well as the complementary study of the novel properties and potential applications of the resulting nanomaterials have been the focal points of my graduate study. Specifically, a modified template-directed technique has been developed, using a double-diffusion setup via a biomimetic crystallization process, which has enabled the successful preparation of various single-crystalline 1D nanostructures, including fluorides, tungstates, sulfides, and phosphates, under ambient, room-temperature conditions, without using either very harmful precursors or solvents, and without generating particularly toxic byproducts. The family of alkaline-earth metal binary and perovskite ternary fluoride nanowires, doped with rare-earth ions, has displayed unique luminescence properties, with applications in optical devices. In addition, the generation of tungstate solid solution 1D nanostructures provides for a fundamental understanding of composition-modulated luminescence properties, leading to key structure-property correlations. A class of multifunctional 1D nanostructures has also been created by merging the favorable luminescent and magnetic properties via incorporating Mn ions into tungstate matrix. Moreover, the validity of this method has been demonstrated for the fabrication of semiconducting metal sulfide nanowires, which show higher photocatalytic degradation activity than their bulk counterparts. Finally, the technique has been extended to the large-scale synthesis of high aspect-ratio phosphate nanowires, which have been tested for their potential applicability as fluorescent labels in molecular imaging. The synthetic approach developed is quite generalized and flexible, and can be applied to the creation of other classes of nanomaterials.

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